Effect of incorporation of cottage cheese whey solids andBifidobacterium bifidumin freshly made yogurt

Abstract

SummaryFresh rennet-coagulated cottage cheese whey was vacuum concentrated to 400 g total solids kg−1, and part of this evaporated whey was acidified to pH 4·6 to prepare whey protein concentrate. Both products were used separately to replace non-fat dried milk in yogurt. Diacetyl concentration increased on fortification with whey protein concentrate, and acetaldehyde increased with evaporated whey. However, the use ofBifidobacterium bifidumas a supplementary starter culture in addition toStreptococcus thermophilusandLactobacillus delbrueckiisubsp.bulgaricusreduced the concentration of diacetyl and acetaldehyde. Incorporation of whey solids stimulated the growth ofStr.thermophilusandBifid. bifidumin yogurt but the count ofLb. bulgaricuswas reduced whenBifid. bifidumwas incorporated. Examination of the organoleptic properties of the yogurts showed that both forms of whey solids were satisfactory replacements for non-fat dried milk. Fortification by whey protein concentrate improved the textural properties. Supplementation byBifid. bifidumhad only a marginal effect on the flavour of the product.